1. Field of the Invention
This invention relates to urea-hydrogen peroxide stabilized towards decomposition in an aqueous or alcoholic solution, and, more particularly, to free-flowing powders of a urea-hydrogen peroxide-PVP product made by a fluid bed process.
2. Description of the Prior Art
Urea-hydrogen peroxide is a well-known commercial product useful as an antiseptic and disinfectant in treatment of wounds, for bleaching hair, and as a readily biodegradable and environmentally safe bleaching agent, detergent and cleaning agent. However, urea-hydrogen peroxide, also known as carbamide-peroxide, is not very stable in aqueous and alcoholic solutions. Several techniques have been used in an attempt to provide stabilized carbamide peroxide solutions; for example, see U.S. Pat. Nos. 2,120,430; 2,430,450; 2,542,898; 3,629,331; 3,657,413; 4,155,738; 4,302,441; 4,514,384; 4,518,583; 4,522,805; 4,607,101; 4,826,681; 4,837,008 and 4,895,875. However, these methods have not been entirely successful; accordingly, it is recommended that carbamide peroxide remain refrigerated during periods of non-use.
Stabilized H.sub.2 O.sub.2 compositions also have found wide utility in commercial and industrial applications, e.g. as an antiseptic, disinfectant, sterilization agent, bleaching material, washing concentrate, etchant, in cosmetic preparations, and as a catalyst in polymerizations requiring a free radical source. In biological applications which require an antiseptic, disinfectant or sterilization agent, such H.sub.2 O.sub.2 compositions require release of an effective amount of oxygen at a desired rate.
Shiraeff, in U.S. Pat. Nos. 3,376,110 and 3,480,557, disclosed that a solid, stabilized hydrogen peroxide composition of hydrogen peroxide and a polymeric N-vinyl heterocyclic compound could be prepared from an aqueous solution of the components. The process involved mixing PVP and a substantial excess of aqueous H.sub.2 O.sub.2 and evaporating the solution to dryness. The H.sub.2 O.sub.2 content of the composition was given as being at least 2%, and preferably 4.5 to 70% by weight. Prolonged drying of the composition, in an attempt to reduce the water content, however, resulted in a substantial loss of H.sub.2 O.sub.2 from the complex. The product was a brittle, transparent, gummy, amorphous material, and had a variable H.sub.2 O.sub.2 content ranging from about 3.20 to 18.07% by weight, depending upon the drying times.
The Shiraeff process did not attain commercial success because (1) the product was not a free-flowing powder and thus could not be handled easily; (2) its water and hydrogen peroxide content varied over a wide range; (3) the complex was not stable; and (4) the aqueous process could not be carried out on a commercial scale.
Merianos, in U.S. Pat. No. 5,008,093 described an improved process for making free-flowing, substantially anhydrous complexes of PVP and H.sub.2 O.sub.2 by reacting PVP and a solution of H.sub.2 O.sub.2 in an anhydrous organic solvent such as ethyl acetate. However, this process required the use of substantially anhydrous H.sub.2 O.sub.2, which was too dangerous to handle industrially.
Rossberger et al., in German Patent OLS 3,444,552, published Jun. 12, 1986, described a process for making urea peroxyhydrate using a fluidized bed of urea having a particle size of less than 1000 .mu.m onto which was sprayed an aqueous solution of concentrated H.sub.2 O.sub.2. This technique was practical only because urea is a stable, crystalline compound which readily formed a free-flowing powdery complex upon addition of aqueous hydrogen peroxide solutions.
Production of free-flowing complexes of PVP-H.sub.2 O.sub.2 from amorphous, polymeric, polyvinylpyrrolidone and aqueous H.sub.2 O.sub.2, however, has not been easy to achieve commercially because, during production, the PVP polymer can alter its physical state, and/or retain excess water and/or free H.sub.2 O.sub.2, even at elevated drying temperatures, resulting in a gummy rather than a free-flowing product.
Accordingly, it is an object of this invention to provide free-flowing powders of urea-hydrogen peroxide-PVP which exhibits stability towards decomposition in aqueous and alcoholic solutions.
Still another object is to provide a free-flowing powders of urea-hydrogen peroxide-PVP made by spraying an aqueous solution of urea-hydrogen peroxide onto a fluidized bed of PVP at a predetermined rate, and drying.
These and other objects and features of the invention will be made apparent from the following description herein.